Cathode ray tubes and apparatus using the same



NOV 14, 1967 I YUKIO KOYANAGI 3,352,970 CATHODE RAY TUBES AND APPARATUS USING THE SAME v F il ed March 27, 1964 4 Sheets-Sheet 1 5 /0' Anode l/o/fage (Kv) ATTORNEYS 196,7 YUKIO KOYANAGI 3,35 ,9 0

CATHODE RAY TUBES AND APPARATUS USING THE SAME Filed March 27, 1964 4 Sheets-Sheet 2 MQ mg Im/an ''ar ya [4 i 0 (o/an; I BMW; ZQM, MWKZ ATTORNEYS Nov. 14, .1967 Yuklo KOYANAGI CATHODI'JBAY TUBES AND APPARATUS USING THE SAME Fi led March 27.1964

4 Sheets-Sheet 5 w w cm a wmk mm g Inuemor yukio ko/anagx ATTORNEYS 'CATHODE RAY TUBES AND APPAiiATUs USING THE SAME" Fild March 27. 19 64 YUKIO KOYAN AGI Nov. 14,1967

4 Sheets-Sheet 4 Fig. '//B I inva er Yukio koyana i 19 ]M, [0M4 7ZLZhMl w ATTORNEYS horrz y t e iro b y ac g an eiectro-c ducti e an the the buib at a osition y to that me oi the eiect beam ar diiir it in the d uorescent screen royided 2 smaiier in order d t e nt screen is rnci' ed at an area oi the du rescent scree c axis oi th eiect n beam the eiectrou-beam spot is made iarge ote iro the n being ing oi the ge resolution the eie tron beam in orde improve the age resoiutron, o e 5 endea o er to so odiiy the eiectron gu to ge smaiier eiectron b a or to decrease the beam c t ca ray hes and The iormer can be accompi' ed by empioyin' such ie ision reee' ers known periodic iocus guns \ectromagnetic i( t 6 present invention pros stem, and the iatter may accompiished, ii m oi reiati eiy smaii h zontai 0 provided ior decreasing e magnitude oi the g power, attrmflafly suita, Xe beam current with raised eiircieucy 0i i 6 fl isio rec i i g set, screen ior obtaining the same brightness oi d an ti t r' t' 5 i 3 or t is pu ose, the present invention pr yides be mad obvious iro th 1. iewing by uman eyes oi the side oi the cm i the went on, m i 35 screen upon which eiectron bea s inge. mg drawings, in PKG. 3, reiative rightnesses are own m; pepyegentafign i some. the s me e ectron bea current ior yariabie how the teievisio ge is preages 0133 View. gsystems- {C in which eiectron be e r pinges metai i am atic repr ntatron s wi a and human eyes iooh at the opposite phosr modriying t con entionai system hown in WW8 5 ior W Whetein a m have the horizontai depth oi he system Provide the rv, curve 6 i i r to the ar the 10:55 Semen, cording o the present invention, whi e diagra wing eiation etween b am d'i ctiy impinges phosphor \ayer Yh reiatiye b ness ior vario iiuores. layer on the op osite side, and hum with o d the ame eiectron-beam meet Y1 i i y Q6 WW6 iar sys e ha g no e back iayer and 6 3 ho the iundamemfl idea that, ior one and the sam rightness y 0 ohm-me can remarhabiy be decrea d with low according to the pr se n ention. ms 0 gthe eiat onb een 5o provision oi a portabie teie rsron re ectron t the fluorescent Xow powe consumption, together w mm) to the mess smaii deflection a e to be desorib As ior exampie, by an arra gemer 9 6mg m rei it ha been confirmed that the bri w the ve-m u iou d iu i u obtained rth an anode oitage oi 5 e ma e bstantiaii iior hrougho t the current 0 15 u is s bstantiaiiy t oi the iiuoresc or rig to the tained w'th 6 h anode oitage ar current 'n a con entionai cathode a curve diagram sho ing t e reiation behe the ron cam impiu angie (a) oi t inciination i orescen screen 9 Y 15 I New 0i ect to the centr X axis oi th tron b m an a bombmdQeme resoiution, f em S and ut it t desrrabie to drspos ii and i7. 0 ow esc nnr g drstor t 1 t h \ace and reme ied accord ng e o e as en The prese in entron conte cent screen out oi the centrz 1 shows a pie a cathode ray tube bui beam when the met is not ing the prese entio by side eie ation A an the d fl t d demo beam 6W1 3', eiectric ireid, as diagramm: G a iront eie atron Xampi oi iiuores P16. 6, i each oi these fr ccording to the rave tion', a d gun, L the fluorescent scre of the cathode ray tube seen from the X-direction, having the minimum volume, and capable of satisfying the above explained various conditions, durable to the atmospheric pressure, and enabling proper viewing of the fluorescent image.

The shape of the cathode ray tube as seen from the Z- direction depends upon the shape of the fluorescent screen to a certain extent. The shape of the fluorescent screen is not necessarily approximately rectangular by the reason hereinafter described, but may be nearly a trapezoid, if necessary. In case when the shape of the fluorescent screen is as shown in FIG. 14, and when it is viewed from the Z'-direction, and if the right-hand end line of the fluorescent screen is considered as having a definite angle of inclination in the X-Z' plane, the line of its intersection with the plane of the glass window decides the shape of the cathode ray tube as seen from the Z-direction. The plane of the window is desirable to be geometrical plane as far as is-allowed by the strength of the glass bulb subjected to the atmospheric pressure, from the standpoint of image distortion, and it is nearly a plane substantially lying in X-Y plane. When the position and shape of the window are decided as above-mentioned, the line of intersection hereinabove referred to becomes line 14 in FIG. 14; Consequently, the shape of the cathode ray tube as seen from the Z-direction is as shown in FIG. 13B.

When the fluorescent screen is trapezoidal with a similar cross-sectional shape of the glass bulb, the glass bulb may have sharp corners providing weak points, as well as, inner places of inconvenient working, such as metal-backing. For this reason, it is desirable to make the fluorescent screen with a rectangular shape.

Referring to FIG. 14, R1 is for providing tolerance in order not to have the inclination of the deflecting system observed clearly by scanning lines, and R2 is decided to prevent the ends of the fluorescent screen from being apparently concaved, when the fluorescent screen of partcylindrical shape is seen from the X-, and Z-directions. R is provided for giving tolerance for neck-shadow. Instead of providing edges as above, an extra electrode may, for example, be disposed within the cathode ray tube for limiting the electron beam after having been deflected to a definite shape.

The upper and lower lateral lengths a and b (see FIGS. 14 and 15) of the fluorescent screen are decided by the extent of electrical compensation by means of the waveshapes of deflecting current or the like, or of magnetic compensation by means of compensating magnets, except optical means for compensation of the shape of the fluorescent screen.

The fluorescent screen is viewed through transparent glass window portion 13 in FIG. 13. This portion must not have any optical distortion, but its color or transparency may be changed if necessary or desirable. On the inner side of the glass window portion 13, there should be provided an electrically-conductive transparent film for the purpose of static shielding. The film should evenly adhere to the inner face of glass portion 13 and it forms an electrostatic capacity between itself and the electroconductive film provided on the outside of the glass bulb except for glass portion 13.

The fluorescent screen is formed on the above-mentioned electro-conductive film and transparent inner film. As shown in FIG. 3, the metal back is not so effective when used at about 5 kv. anode voltage, and consequently, the metal back may be omitted in order to simplify manufacturing steps. When the anode voltage is higher, the metal back is effective and may advantageously be employed. When the anode voltage is sufficiently low, the fluorescent screen may be formed directly on the bulb glass.

In order to compensate for the trapezoidal distortion hereinbefore described by virtue of deflection, it is difficult to accomplish the required compensation into good linearity by the electrical method of compensation only to a large extent. It is, therefore, considered to effect the required compensation by combination of electrical compensation and optical compensation, or solely by optical compensation.

Assuming that the shape of the raster on the fluorescent screen is as shown in FIG. 15, having lateral widths a and b, and height h, with the apparent center of deflection M, the center of fluorescent screen 0, and the length l of W, with angle of inclination 0 of the fluorescent screen relative to its axis (71W, an optical magnifying system of focal length f=57 may be provided on the axial line inclined to the fluorescent screen by an angle 0 the distance between focal point F and point 0 being P. When no electric or magnetic deflection correcting means is provided in the cathode ray tube, the raster on the fluorescent screen will be distorted. The relation between the lengths a on the upper edge A of the screen and b on the lower edge B of the screen is defined by:

On the other hand, the magnification m1 at the upper edge A and m2 at the lower edge B by the optical magnifying system are:

P+ b cos 0 Therefore, to compensate for the trapezoidal or keystone distortion, the arrangement has to satisfy the following:

1+2 cos 6 P+2 cos 0 Z-b cos 0 Ph cos 0 then,

1 cos 0,

F cos 0 (17) is obtained. Thus, the arrangement will be free from key stone distortion when the relationship defined .by Equation 17 is established therein. Various kinds of optical magnification may be used, among which concave mirrors and convex lenses are utilized, in general.

It has now been understood that, according to the present invention, the cathode ray tube may be of simple construction with a relatively small horizontal depth, suitable for use in a portable television receiver, and the like. In addition, its power consumption is low, while its image resolution is good. If it is combined with an optical magnifying system, as a Fresnel lens, with the axis of the optical system inclined to the vertical axis of the fluorescent screen, electrical compensation of the deflection can easily be effected, and also easy-viewing of a fluorescent image is obtained.

What we claim is:

1. A cathode ray tube comprising a closed glass bulb, an electron gun at one end of said bulb directing an electron beam along a central axial line of said bulb to a portion of the inner surface at opposite end of said bulb, an electroconductive film layer on said inner surface of said bulb at a position out of alignment with but adjacent to the central axial line of said electron beam at said opposite end of said bulb, a fluorescent screen provided on said film layer, said fluorescent screen being inclined to said axial line at an acute angle with the side edge of said fluorescent screen which is the most remote from said electron gun being positioned closely adjacent said central axial line of said electron beam, the shape of a vertical section of said screen in a plane containing said central axial line of the electron beam being a circular arc the center of which is at the point of intersection of a circle passing through the opposite ends of said section and the apparent center of electron beam deflection, and the perpendicular bisecting line to a line connecting said opposite ends of the fluorescent screen passing through said center, and the radius of said circular are being equal to the length of a straight line connecting said point of intersection to one end of said fluorescent screen.

2. A cathode ray tube apparatus comprising a cathode ray tube, said tube comprising a closed bulb having an electron gun therein, said gun projecting an electron beam at a portion of the inner surface of said bulb spaced therefrom along a central axial line of said electron beam, an electroconductive film layer on said inner bulb surface adjacent the point where said electron beam impinges on said inner surface, and a fluorescent screen provided on said film layer, said fluorescent screen being inclined to the axial line of said electron beam at an acute angle with the side of said fluorescent screen remote from said electron gun being positioned near said central axial line of 8 said electron beam, an optical system disposed inclined to said fluorescent screen for compensating for the trapezoidal distortion of raster, said optical system being formed by an optical lens satisfying an equation References Cited UNITED STATES PATENTS 2,260,228 10/1941 Moller 8857 2,538,852 7/1951 Szegho 1787.85 2,842,711 7/1958 Frenkel 315 2,967,262 1/1961 Madey 315 3,299,314 l/1967 Yamada 315 JOHN W. CALDWELL, Acting Primary Examiner.

DAVID G. REDINBAUGH, Examiner.

J. A. ORSINO, Assistant Examiner. 

2. A CATHODE RAY TUBE APPARATUS COMPRISING A CATHODE RAY TUBE, SAID TUBE COMPRISING A CLOSED BULB HAVING AN ELECTRON GUN THEREIN, SAID GUN PROJECTING AN ELECTRON BEAM AT A PORTION OF THE INNER SURFACE OF SAID BULB SPACED THEREFROM ALONG A CENTRAL AXIS LINE OF SAID ELECTRON BEAM, AN ELECTROCONDUCTIVE FILM LAYER ON SAID INNER BULB SURFACE ADJACENT THE POINT WHERE SAID ELECTRON BEAM IMPINGES ON SAID INNER SURFACE, AND A FLUORESCENT SCREEN PROVIDED ON SAID FILM LAYER, SAID FLUORESCENT SCREEN BEING INCLINED TO THE AXIAL LINE OF SAID ELECTRON BEAM AT AN ACUTE ANGLE WITH THE SIDE OF SAID FLUORESCENT SCREEN REMOTE FROM SAID ELECTRON GUN BEING POSITIONED NEAR SAID CENTRAL AXIAL LINE OF SAID ELECTRON BEAM, AN OPTICAL SYSTEM DISPOSED INCLINED TO SAID FLUORESCENT SCREEN FOR COMPENSATING FOR THE TRAPEZOIDAL DISTORTION OF RASTER, SAID OPTICAL SYSTEM BEING FORMED BY AN OPTICAL LENS SATISFYING AN EQUATION 